Stabilization of fuel oil contaminated soil—A case study

Fuel oil contamination brings adverse effect on basic geotechnical properties of foundation soil. The present study pertains to one such case, from the petrochemical complex near Vadodara City in Gujarat State, India. Here, the fuel oil contaminated soil samples exhibit drastic changes in their geotechnical parameters. Noteworthy among such deleterious changes are: decrease in maximum dry density (–4%), cohesion (–66%), angle of internal friction (–23%) and unconfined compressive strength (UCS) (–35%) and increase in liquid limit (+11%). An attempt has been made to stabilize the contaminated soil using various additives viz., lime, fly ash and cement independently as well as an admixture of different combinations. It is apparent from the test results that the stabilization agents improved the geo-technical properties of the soil by way of cation exchange, agglomeration, and pozzuolanic actions. The best results were observed when a combination of 10% lime, 5% fly ash and 5% cement was added to the contaminated soil. The improvement in unconfined compressive strength (UCS), cohesion and angle of internal friction can be attributed to neo-formations such as Calcium Silicate Hydrates (CSH, CSH-1) that coats and binds the soil particles. Formation of stable complex between oil and metallic cations, results in reduction of leachableoil.     

Feldspar Alteration and Diagenetic Characteristics of the Parsora Sandstones, Son Basin, India

Moderate to poorly sorted immature Parsora sandstones rich in K-feldspar show much of the feldspar during early diagenesis transformed to kaolinite after prolonged interaction with acidic pore solutions. The kaolinitic epimatrix formed and was later partially or wholly converted as an orthomatrix producing chert-phyllosilicate assemblage. Ferric oxide, bleached biotite, kaolinite and quartz cement denote an oxy-acidic early diagenetic environment. Late diagenesis involved neoformation of primary or secondary matrix, illitisation of montmorillonite and muscovite authigenesis. The high pressure-temperature regime required for these transitions resulted from tectonic activity during Triassic-Jurassic times. Carbonate-chlorite appeared late in the sediments denoting an alkaline-reducing condition at the late part of the diagenesis. Finally, the secondary porosity developed through carbonate dissolution was later filled up with allochemical ferric iron cement receiving ions from the percolating meteoric water.